import?java.util.*;
import?java.lang.*;
import?java.awt.*;

/**
?*?Decode?handles?the?operation?for?the?decode?stage?of?pipelined?execution.
?*/
class?Decode?extends?Stage?{
	/**
	?*?holds?the?Rd?of?the?last?three?instruction?to?detect?hazards
	?*/
????private?Vector?hazardList;
????/**
	?*?placeholder?for?an?instruction?that?is?stalled.
	?*/
????private?Instruction?instructionSave;
????/**
	?*?saves?the?program?counter?for?an?instruction?that?is?stalled.
	?*/
????private?int?savePC;
????/**
	?*?indicates?that?a?stall?has?been?issued.
	?*/
????public?boolean?isStall;
????/**
	?*?indicates?that?a?stall?has?been?detected.
	?*/
????public?boolean?stallflag;
????/**
	?*?indicates?whether?branches?are?assumed?taken?（not?used）.
	?*/
????public?boolean?assumeBranchTaken;
????/**
	?*?indicates?whether?a?branch?instruction?was?taken?on?its?last?execution.
	?*/
????public?boolean?branchPrediction;
????/**
	?*?indicates?whether?forwarding?is?used.
	?*/
????public?boolean?forwarding;
????/**
	?*?table?used?to?predict?branches?（unused）.
	?*/
????public?Vector?branchTable;?

????/**
	?*?initialzes?the?fields?of?the?object
	?*/
????public?Decode（）?{
???????super（）;
???????instructionSave?=?new?Instruction（“NOP“）;
???????isStall?=?false;
???????assumeBranchTaken?=?true;???//?assume?branches?always?taken?（when?prediction?disabled）
???????hazardList?=?new?Vector（3）;
???????branchTable?=?new?Vector（）;
???????hazardList.addElement（new?Integer（0））;
???????hazardList.addElement（new?Integer（0））;
???????hazardList.addElement（new?Integer（0））;
????}

????/**
	?*?process?the?current?instruction.??Implements?the?functionality?of?the?decode?stage?of?a?pipeline.
	?*?Uses?a?vector?of?instructions?each?of?the?other?pipeline?stages?the?register?file?and?the
	?*?ListBoxes?object.
	?*?@see?Instruction
	?*?@see?Fetch
	?*?@see?Execute
	?*?@see?Memory
	?*?@see?WriteBack
	?*?@see?MemoryType
	?*?@see?Listboxes
	?*/
????public?void?step（Vector?Instructions?MemoryType?regFile?
?????????????????????Memory?myMemory?WriteBack?myWriteBack
?????????????????????Fetch?myFetch?Execute?myExecute?ListBoxes?lb）?{

?????????String?str;

????????//?if?last?instruction?was?stalled?recall?stalled?instruction

????????if?（PC==Instructions.size（））
???????????PC?=?-9;??//?this?is?actually?a?NOP?received?from?Fetch

????????if?（isStall?==?true）?{?????????????????????????????
????????????myInstruction?=?instructionSave;???
????????????PC?=?savePC;
????????}
????????
????????//--Check?for?RAW?hazards?in?pipeline;?ignore?NOP?instructions-----

????????//?check?RAW?hazard?for?rs

????????stallflag?=?false;
????????if?（?（?（?（myExecute.myInstruction.opcode?!=?0）?&&?
???????????????（myExecute.myInstruction.flush?==?false）?&&
???????????????（myInstruction.rs==
????????????????（（Integer）?hazardList.elementAt（0）?）.intValue（）?））?||??
??????????????（?（myMemory.myInstruction.opcode?!=?0）?&&?
???????????????（myMem

?屬性????????????大小?????日期????時間???名稱
-----------?---------??----------?-----??----
?????文件???????10904??2000-08-11?10:11??Decode.java
?????文件????????6595??2000-08-11?10:11??Execute.java
?????文件????????1819??2000-08-11?10:11??Fetch.java
?????文件???????10524??2000-08-11?10:12??GUI.java
?????文件????????2602??2000-08-11?10:12??Help.java
?????文件????????9895??2000-08-11?10:12??Instruction.java
?????文件????????4451??2000-08-11?10:12??ListBoxes.java
?????文件????????2737??2000-08-11?10:12??Memory.java
?????文件????????1168??2000-08-11?10:13??MemoryType.java
?????文件????????4202??2000-08-11?10:13??Simulator.java
?????文件?????????843??2000-08-11?10:13??Stage.java
?????文件????????5679??2000-08-11?10:13??Stages.java
?????文件????????2578??2000-08-11?10:13??UI.java
?????文件????????3772??2000-08-11?10:13??WriteBack.java
?????文件????????7187??2000-09-07?12:08??mips.html